1. Field of the Invention
This invention relates to a novel tube expander capable of simultaneously applying a plurality of selected radial pressures outwardly at a plurality of sections of a tube interior to provide selected expansions of said sections of said tube.
2. Description of the Prior Art
It is old to apply a radial force outwardly from the interior of a tube at a selected portion thereof in order to permanently enlarge the diameter of said selected portion of said tube. This is often done, for example, in sealing tubes-to-tubesheets in heat exchangers by expanding that portion of the tube within the hole, or opening, of the tubesheet beyond its elastic limit. Such a procedure is illustrated in "Heat-exchanger tube-to-tubesheet connections" by Stanley Yokell in Chemical Engineering, Feb. 8, 1982, pages 78 to 94. In some cases, for example, when the tube is welded to the tubesheet, it may be desirable also to expand that portion of the tube extending immediately beyond the stub lying within the opening in the tubesheet. To do this using the tube expanders discussed by Stanley Yokell would require a two-step process. After expanding that section of the tube within the hole in the tubesheet, the tube expander would then be moved to that portion of the tube immediately beyond the stub lying within the hole in the tubesheet, and the procedure would be repeated. I have found that by using the novel tube expander defined and claimed herein, a plurality of selected radial pressures can be simultaneously applied on selected sections of the tube interior to obtain controlled tube expansions of said selected sections with little or no adverse effects to the tube, the tubesheet or the weld joining the two.